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GCHQ to encrypt your tweets with Enigma - for science

Now you can make even less sense on Twitter

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The Enigma code, once used by the Nazis to send secret military commands, will be used by visitors to the Cheltenham Science Fair next week to send tweets.

In a celebratory code-cracking session to mark 100 years since Alan Turing's birth, GCHQ has lent out one of its Enigma coding machines to the Science Fair from 12 to 17 June and is inviting members of the public to encrypt their social networking messages.

The coded messages will be sent to Bletchley Park and then decoded with the Bombe machine, which Turing invented to crack the code.

The Enigma code was developed by the Germans just after the WWI and was initially cracked by the Polish before the German military added extra layers of complexity.

Enigma machines scramble plain-text messages entered through the keyboard with a series of rotating 'wheels' or ‘rotors’, turning them into incoherent ciphertext. The machine's variable elements can be set in many billions of combinations - each one will generate a completely different ciphertext message.

If the recipient knows how the machine has been set up, they can type the ciphertext back in and it will unscramble the message. Without the Enigma setting, the message remains indecipherable.

Working out that no letter could ever be represented as itself, allowing for mistakes in operator messages as well as the eventual invention by Turing of the Bombe code cracker all contributed to the British finally breaking the encryption in 1940.

The messages sent from Cheltenham and decoded in Bletchley Park will be tweeted back to the Science Fair. ®